Thymus Leukemia Research Articles

The immunosuppressive capacity of alloantisera in mice, including sera directed primarily against thymic antigens

Alloantisera prepared in inbred mice and directed against H-2 histocompatibility differences or against the thymic antigens θC3H and TL (thymus leukemia) were assayed for their immunosuppressive action when injected in mice against whom the alloantisera were directed. There was a significant depression of the reactions to bovine serum albumin (BSA) and sheep erythrocytes (SRBC) as determined for BSA by passive hemagglutination and by direct hemagglutination of SRBC. Plaque production (measured by the Jerne plaque assay) against SRBC was also inhibited. The mice exhibited leukopenia, and in one experiment there was a significant increase in the number of takes of syngeneic tumor transplants in antiserum-treated mice given a subthreshold inoculum of tumor cells.

Implications of TL phenotype changes in an H-2-loss variant of a transplanted H-2b-H-2a leukemia.

An H-2-loss variant line, lacking H-2(a) antigens, was obtained from an H-2(b)/H-2(a) (C57BL x A)F(1) transplanted leukemia by immunoselection. The TL phenotype of the unselected line was TL.1,2,3,4 and that of the variant TL.1,2,4, which is the phenotype of TL(+) leukemias of C57BL. This finding, and the observed quantitative alterations of antigens TL.1,2 and 4, indicate that the Tla (Thymus leukemia antigen) locus was functionally deleted together with the H-2 locus in the process of variant formation, despite absence of selection against cells carrying TL antigens. Representation of H-2 antigens of the remaining haplotype, H-2(b), was quantitatively unchanged.

Serological analysis of thymus and spleen grafts

Thymus and spleen grafts from neonatal C57BL mice were implanted beneath the kidney capsule of (A x C57BL) F1 hybrids. At various intervals after implantation, the grafts were analyzed serologically. Cells of each graft were tested for the presence of cells of host origin, TL (thymus-leukemia) antigenicity, and sensitivity to the cytotoxic effect of guinea pig serum (GPS). Thymus grafts showed partial repopulation by host cells 11 days after grafting, and some grafts were completely repopulated by host cells 13 days after grafting. All thymus grafts were fully repopulated 18 days after grafting. With one exception, thymus grafts contained no significant number of TL-positive cells within 14 days after grafting. TL-positive cells appeared in thymus grafts examined 15 days after implantation, and their number increased up to the 18th day after implantation. Cells residing in thymus grafts remained sensitive to GPS throughout the period of observation. The acquisition of thymus-distinctive serological properties by host cells repopulating thymus grafts was similar in intact and in thymectomized recipients. Spleen grafts were completely repopulated by host cells as early as 8 days after grafting. The cells residing in spleen grafts remained TL-negative throughout the period of observation, and were refractory to the cytotoxic effect of GPS. It is thus apparent that, while both spleen and thymus grafts are invaded by TL-negative cells, only those entering the thymus acquire the antigen. The nature of the process by which the thymus endows thymus-distinctive properties on cells entering it is discussed.

Modulation of TL (Thymus-Leukemia) Antigens by Fab-Fracments of TL Antibody

Summary Cytotoxic antibodies of H-2 and TL specificities were located in the same 7 S γ-globulin fraction of mouse antiserum. The anti-TL and anti-H-2 activities occurred together in antiserum fractions prepared by Sephadex G 200 gel filtration or by electrophoresis in a Geon block. The modulating activity of TL antiserum (i.e., its capacity to cause the TL + → TL - phenotypic change in cells exposed to the antiserum in the absence of lytic C′) also occurred in the 7 S γ-globulin fraction. When γ-globulin prepared from antiserum by Geon block electrophoresis was digested with papain, cytotoxic activity of both H-2 and TL specificities was lost, but TL modulating activity remained. Thus attachment of univalent TL antibody fragments (Fab) lacking the complement-fixing and other biologic properties of the Fc-fragment was sufficient to induce modulation. Papain digests of H-2 antibody prepared in the same way did not induce modulation of H-2 antigen or of TL antigen, indicating further that modulation of TL antigen is a specific response to TL antibody.

Ly-A and Ly-B: two systems of lymphocyte isoantigens in the mouse.

Two systems of isoantigens confined to thym ocytes and lymphocytes have been defined in the mouse by cytotoxic isoantisera. The two genetic loci have been designated Ly-A and Ly-B . Typing of 25 mouse strains and sublines indicates that each system comprises only 2 alleles, determining alternative isoantigens Ly-A. 1 or Ly-A. 2, and Ly-B. 1 or Ly-B. 2, respectively. There is no evidence of multiple alleles or that either locus is compound. Tests for genetic linkage were performed by serological typing of mice from segregating generations. None of the four loci H -2 (group IX ), θ, Ly-A and Ly-B is closely linked to any other of the four. Ly antigens are found in high concentration on thymocytes and in lesser amounts on lymphocytes. The small absorptive capacity of bone marrow cell suspensions is probably due to the presence of mature lymphocytes rather than thymocyte-lymphocyte precursors, which according to preliminary evidence lack Ly antigens. Ly-B. 1 is exceptional in that the disparity between thymocytes and lymphocytes in content of antigen is greater than that of the three other antigens. When Ly antiserum is injected into mice of the relevant Ly type, under conditions which give complete absorption of H-2 antibody in vivo , Ly antibody is not extensively absorbed ; this is to be expected from the limited tissue distribution of Ly antigens. Absorption of Ly and θ iosantibodies in vivo is reduced by treatment of the recipients with cortisone or lethal total-body irradiation. The reduction in titre of Ly and θ antibodies in such mice may be no more than that resulting from dilution. Absorption of injected H-2 antibody also may be reduced by treatment of the recipients with cortisone but in this case the effect of corti­sone does not approach the virtual abolition of absorption that is seen with Ly and θ anti­bodies. The thymocytes and lymphocytes of chimeras formed by restoring lethally irradiated mice with allogeneic bone marrow have the Ly-A type, Ly-B type and θ type o f the donor. The content of Ly antigens on cells of different leukaemias varies widely and shows no correlation with presence or absence of TL (thymus-leukaemia) antigen; TL + leukaemias may be Ly — or Ly + and TL — leukaemias may be Ly — or Ly + . Five systems of isoantigens are now demonstrable on mouse thymocytes by means of cytotoxic isoantisera. Of these, TL is an exclusively thymic antigen. Ly-A and Ly-B antigens occur also on lymphocytes. θ occurs on thymocytes, on lymphocytes, and in brain. The fifth antigen, H-2. is still more widely distributed and differs from the other four in being repre­sented less strongly on thymocytes than on lymphocytes.

Serological analysis of thymus and spleen grafts.

Thymus and spleen grafts from neonatal C57BL mice were implanted beneath the kidney capsule of (A x C57BL) F(1) hybrids. At various intervals after implantation, the grafts were analyzed serologically. Cells of each graft were tested for the presence of cells of host origin, TL (thymus-leukemia) antigenicity, and sensitivity to the cytotoxic effect of guinea pig serum (GPS). Thymus grafts showed partial repopulation by host cells 11 days after grafting, and some grafts were completely repopulated by host cells 13 days after grafting. All thymus grafts were fully repopulated 18 days after grafting. With one exception, thymus grafts contained no significant number of TL-positive cells within 14 days after grafting. TL-positive cells appeared in thymus grafts examined 15 days after implantation, and their number increased up to the 18th day after implantation. Cells residing in thymus grafts remained sensitive to GPS throughout the period of observation. The acquisition of thymus-distinctive serological properties by host cells repopulating thymus grafts was similar in intact and in thymectomized recipients. Spleen grafts were completely repopulated by host cells as early as 8 days after grafting. The cells residing in spleen grafts remained TL-negative throughout the period of observation, and were refractory to the cytotoxic effect of GPS. It is thus apparent that, while both spleen and thymus grafts are invaded by TL-negative cells, only those entering the thymus acquire the antigen. The nature of the process by which the thymus endows thymus-distinctive properties on cells entering it is discussed.

Modification of the antigenic structure of the cell membrane by thymus-leukemia (TL) antibody.

Modification of the antigenic structure of the cell membrane by thymus-leukemia (TL) antibody.

Mouse isoantigens: separation of soluble TL (thymus-leukemia) antigen from soluble H-2 histocompatibility antigen by column chromatography.

Mouse H-2 histocompatibility antigen has been extracted, solubilized, and partly purified from the cells of an A strain spontaneous leukemia carrying TL (thymus-leukemia) antigens. H-2 and TL. 1, 2, 3 activities were measured by inhibition of the cytotoxic effect of the corresponding isoantibodies. TL activity was associated with the H-2 active fraction obtained by solubilization and fractionation by gel filtration. TL specificity was largely separated from H-2 antigen by subsequent chromatography on DEAE Sephadex as an adjacent component in a series of fractions. The soluble H-2 antigen prepared from the leukemia cells was tested for most of the specificities determined by H-2(a) with no exceptional results. TL. 1, 2, 3 activities, measured as each component separately, were located in approximately the same position; there is no clear indication yet whether the three TL specificities are separable from one another. It appears that in addition to the close genetic linkage between the H-2 and TL loci, and their reciprocal interaction in producing H-2 and TL antigens, these antigens exhibit some similarity at the chemical level.

Conditions affecting the inhibitory action of RLP on radiation leukaemogenesis in mice.

The inhibitory effect of RLP (a cell-free extract derived from sheep spleen) on radiation leukaemogenesis in mice, was studied under different biological conditions, in order to determine the limitations and specificity of its action. For inhibition of radiation leukaemogenesis (lymphatic, thymic, type) in C57BL/6/Jax mice, the RLP injections were required to be given repeatedly — at least 4 times for demonstrable effect, and 10 times for optimal effect — the treatment begun about 1 hour after irradiation. Weaker effects were obtained when the treatment was begun 24 hours after irradiation, and no inhibition when the injections were given before the start of the radiation treatment, or begun 2 weeks after its completion. In irradiated RF mice, RLP inhibited the induction of lymphatic (thymic) leukaemia, while that of myelogenous leukaemia appeared to be augmented. RLP failed to inhibit the spontaneous development of the lymphatic (thymic) leukaemia in AKR mice. The results support the conclusion that the inhibitory action of RLP is an anti-radiation effect with respect to leukaemogenesis, rather than an antagonism against the leukaemogenic process proper.

LEUKEMOGENIC ACTIVITY OF CELL-FREE FILTRATES OF RADIATION-INDUCED LEUKEMIA OF RF MICE.

The incidence of leukemia in the RF mice exposed to a single whole body irradiation of 350 r X-rays was 77.4%, 41 out of 53 mice. Of them, 20 animals developed the thymic type and 20 others the non-thymic type lymphocytic leukemia, while only one developed myelogenous leukemia. Comparative studies were made on the thymic and non-thymic type leukemia. By inoculating the cell-free filtrates from the leukemic RF mice induced by a single whole body X-irradiation to the newborn mice of the same strain younger than 16 hours old, two (16.7%) of the twelve inoculated animals developed leukemia 375 and 374 days respectively after the inoculation. In the inoculation of the cell-free filtrates from normal mice to the newborn mice of the same strain, and in the non-irradiated control mice not a single case of leukemia developed. On the basis of these findings a discussion has been made on the role of virus in the induction of leukemia by X-ray irradiation.

Antigenic Properties of Experimental Leukemias. II. Immunological Studies <italic>In Vivo</italic> With C57BL/6 Radiation-Induced Leukemias<xref ref-type="fn" rid="FN2">2</xref>

The serum of C57BL/6 mice immunized against an A strain TL+ (thymus leukemia antigen) spontaneous leukemia was highly cytotoxic for the cells of several C57BL/6 leukemias. Paradoxically, this was not associated with resistance in vivo to the inoculation of 2 TL+ C57BL/6 radiationinduced leukemias highly sensitive to TL antisera in vitro. Leukemia cells recovered aftei their outgrowth in immunized C57BL/6 mice lost their sensitivity to TL antisera in vitro and their ability to absorb specific cytotoxic activity from TL antisera. A single further passage of these cells in normal untreated C57BL/6 hosts was accompanied by complete restoration of sensitivity, even after 3 consecutive passages in immunized hosts. Immunoselection, inadequate complementation, or interference by blocking antibody might account for the outgrowth of TL+ leukemia cells in immunized hosts, but the present evidence does not favor these interpretations. More probably the temporary changes in antigenicity reflect an adaptational alteration affecting the entire population of leukemia cells. (auth)

Chromosomal Patterns of Irradiated Leukemic and Nonleukemic C57BL/6J Mice<xref ref-type="fn" rid="FN1">2</xref>

Chromosomes of 17 C57BL/6J mice receiving 600 r totalbody x irradiation were analyzed and compared to chromosomes of 6 normal mice. Seven mice developed leukemia and 10 did not. Chromosomes of 4 leukemic mice were examined. Mouse #1 (generalized leukemia) had cells with a mode of 40, variation above the mode, and a large marker chromosome. Mouse #2 (localized thymic leukemia) had 2 hyperdiploid modes of 41 and 42 in thymic tissue, but normal chromosomes were in the spleen and marrow. Mouse #3 (generalized leukemia) had modes of 40 and 41 in the thymus, spleen, and marrow. Mouse #4 (localized thymic leukemia) had a modal number of 41 with variation about the mode. One of the 10 irradiated nonleukemic mice had some cells with a pseudodiploid karyotype containing a minute chromosome, and another had a questionable abnormality consisting of increased variation about the mode. The remaining 8 mice had normal chromosomes. Aneuploidy in irradiated nonleukemic mice may be due to preleukemia or to persistent x-ray induced aberrations. The possibility of persistent chromosomal alterations after x ray suggests irradiation leukemias are not ideal for evaluation of the significance of aneuploidy in mouse preleukemia or leukemia. (auth)

Pathogenesis of mouse viral leukemia.

Summary and conclusions1. Incidence of thymic leukemia in AK/Z mice injected as newborns with Gross leukemia virus(agent A) was 90% and the peak incidence of the disease occurred at 3-4 months of age. Incidence of leukemia in the controls was 73% with a peak occurrence at 8-12 months. 2. Thymuses from 52 sacrificed virus-injected AK/Z mice were examined at 13-72 days of age. No gross or microscopic abnormality was noted until about SO days, when multiple foci of medium to large lymphocytes appeared in the cortex. These foci rapidly became confluent and at about 70 days of age, the thymus was transformed into a lymphomatous tumor. 3. Bioassays of 22, 57-74 day old thymuses from virus-injected mice disclosed autonomous leukemic cells in 10. Correlation of microscopic and bioassay diagnosis of malignant transformation was somewhat below 100%. Some thymuses, which were judged to be leukemic “in situ”, were not transplantable. 4. Bioassays indicate the presence of virus in non-leukemic thymuses of virus-inject...